English

A device to indicate the direction from which the WIND blows. Also called weather vane, wind vane. See ANEMOMETER. A SIGHT on an instrument used for observing BEARINGS, as on a PELORUS, BEARING CIRCLE, etc. Also called sight (or sighting) vane. A device to indicate the direction toward which the CURRENT flows.

In PHOTO­GRAMMETRY, the straight line on a PHOTOGRAPH upon which lie all the VANISHING POINTS of all systems of parallel lines parallel to one plane.

In PHOTO­GRAMMETRY, the IMAGE in the plane of a PHOTOGRAPH, of the point toward which a system of parallel lines in the object space conver­ges.

A variate is a quantity that may take on any of the values of a specified set with a specified relative frequency or probability often known as random variable. It is to be regarded as defined not merely by a set of permissible values, but by an associated frequency (probability) function expressing how often those values appear in a given situation.

The angle between the MAGNETIC and GEOGRA­PHICAL MERIDIANS at any place, expressed in DEGREES east or west to indicate the direc­tion of MAGNETIC NORTH from TRUE NORTH. Also calledmagnetic variation,or magnetic declination.

Angular difference in direction bet­ween GRID NORTH and MAGNETIC NORTH. It is measured east or west from GRID NORTH. Also called grivation, or grid magnetic angle.

A sedimentary DEPOSIT, bed, or lamination depo­sited in one season. It is usually distinguished by colour or composition and used as an index to changes in the depositional environ­ment.

A stereoscopic PHOTOGRAPH composed of two superimposed IMAGES which polarize light in planes 90° apart. When these IMAGES are viewed through polaroid spectacles with the polarization axes at right angles, an impression of depth is obtained.

Direct connection between two points, either given as two sets of coordinates (points), or by direction and distan­ce from one given set of coordina­tes; or a point in a vector space defined by one set of coordinates relative to the origin of a coordinate system.

A narrow LEAD or lane in PACK ICE. In mineralogy, a crack or fissure in the ROCKS of the EARTH's CRUST in which highly heated waters from below have deposited from solution crystalline minerals (espe­cially vein quartz) and, under certain circum­stances, metallic minerals of economic importance.